Upper crustal deformation in continent-continent collision: A case study from the Bernard nappe complex (Valais, Switzerland)

Scheiber, Thomas; Pfiffner, Othmar-Adrian; Schreurs, Guido (2013). Upper crustal deformation in continent-continent collision: A case study from the Bernard nappe complex (Valais, Switzerland). Tectonics, 32(5), pp. 1320-1342. American Geophysical Union, European Geophysical Society 10.1002/tect.20080

[img]
Preview
Text
scheiber_pfiffner.pdf - Published Version
Available under License Publisher holds Copyright.
Sherpa/Romneo: Publisher's version/PDF must be used in Institutional Repository 6 months after publication

Download (19MB) | Preview

The Penninic nappes in the Swiss Alps formed during continental collision between the Adriatic and European plates in Cenozoic times. Although intensely studied, the finite geometry of the basement-bearing Penninic nappes in western Switzerland has remained a matter of debate for decades (e.g., “Siviez-Mischabel dilemma”) and the paleogeographic origin of various nappes has been disputed. Here, we present new structural data for the central part of the Penninic Bernard nappe complex, which contains pre-Permian basement and Permo-Mesozoic metasedimentary units. Our lithological and structural observations indicate that the discrepancy between the different structural models proposed for the Bernard nappe complex can be explained by a lateral discontinuity. In the west, the presence of a Permian graben caused complex isoclinal folding, whereas in the east, the absence of such a graben resulted mainly in imbricate thrusting. The overall geometry of the Bernard nappe complex is the result of three main deformation phases: (1) detachment of Mesozoic cover sediments along Triassic evaporites (Evolène phase) during the early stages of collision, (2) Eocene top-to-the-N(NW) nappe stacking (Anniviers phase), and (3) subsequent backfolding and backshearing (Mischabel phase). The southward localized backshearing is key to understand the structural position and paleogeographic origin of units, such as the Frilihorn and Cimes Blanches “nappes” and the Antrona ophiolites. Based on these observations, we present a new tectonic model for the entire Penninic region of western Switzerland and discuss this model in terms of continental collision zone processes.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Institute of Geological Sciences
08 Faculty of Science > Institute of Geological Sciences > Tectonics

UniBE Contributor:

Scheiber, Thomas; Pfiffner, Othmar-Adrian and Schreurs, Guido

Subjects:

500 Science > 550 Earth sciences & geology

ISSN:

0278-7407

Publisher:

American Geophysical Union, European Geophysical Society

Language:

English

Submitter:

Guido Schreurs

Date Deposited:

11 Aug 2014 10:50

Last Modified:

13 Dec 2014 04:36

Publisher DOI:

10.1002/tect.20080

Uncontrolled Keywords:

Alpine tectonics, Penninic nappes, Bernard nappe complex, Siviez-Mischabel nappe

BORIS DOI:

10.7892/boris.48588

URI:

https://boris.unibe.ch/id/eprint/48588

Actions (login required)

Edit item Edit item
Provide Feedback